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User blog:Samuli.seppanen/Replacement field-frames and bars for the arms
Quickly after the initial shots I got annoyed by my old field-frames and washers for a number of reasons: * Washers could move 2-3 mm inside the field-frame rings. This made locking the washers with pins after rotating them somewhat challenging. * The washer cores were not perfectly round, and some could take more cord than others. Also, as the sides of the core were straight and they were full of spring cord, the cords could be damaged by the edge of the washer. * The curves in the curved field-frame bars were too deep. This meant that the bowstring had to absorb all the residual energy in the arms after the bolt had left, as the energy was not transmitted to the spring bundle through the hoop in the arm, and the curved field-frame bar. * The field-frames were full of ugly ad hoc fixes, such as welded reinforcements in the bars. * One of the field-frame rings was slightly tilted to one side. * The field-frame bars were welded to the rings, instead of riveted, due to an earlier mistake in punching the holes to the field-frame rings. I also suspected the hooks in the arms were too thick and heavy. Due to all this I decided to make entirely new field-frames, washers and two pairs of hooks from thinner steel. In my experience, version 1 of anything usually sucks, version 2 is fairly good and version 3 is near perfect. I hope that this time I can skip version 2 entirely :). As a reference, here's one old, armed field-frame, the latest version of the arm and a new, lighter hook: Anyways, during my latest ~3 day session at the forge last week I managed to get most of the new parts finished. Here's a picture as a proof: This time the field-frame bars have been cut and grinded from 8,2mm unhardened spring steel(*) instead of being forged like the previous ones. The reasons for doing this are manyfold, but have to do with the manufacturing technique of the Gornea field-frames. The washer cores have been forged from ~3 mm steel plate, and the rest of parts from (concrete) reinforcement steel. For the washer rims I used 10 mm steel, although 8-9 mm would have been sufficient. For the field-frame rings I used 13 mm steel, which is near perfect. I also forged the rings oval this time, as it makes achieving an exact fit very easy. Some of the parts still need fixes, and a new claw and second pair of hooks is still missing. This means I have to visit the forge again next weekend. I've also updated the wiki with articles describing a new technique for forging the washer rims and field-frame bars: * Making a horizontal ring forging template * Forging rings using a horizontal ring forging template (*) Primarily because I have tons of it lying around Category:Blog posts Category:Backup Category:Practical Category:Cheiroballistra Category:Field frame Category:Washer